This invention relates to a dishwashing detergent composition for use in dishwashing machines.
It is well known that strongly alkaline solutions have been used in institutional and household dishwashing machines for washing dishes, glasses, and other cooking and eating utensils. Ordinary tap water is customarily used with a cleaning composition to form a cleaning solution and for rinsing purposes subsequent to the cleaning operation. However, spotting on dishes and glassware by inorganic salt residues and precipitates has been a major problem. In the past these problems were at least partially solved in machine dishwashing detergent compositions by the use of phosphorus compounds. However, they are now strenuously objected to on ecological grounds.
In order to eliminate or reduce phosphate requirements in machine dishwashing detergents more recent patents have found a need to resort to the use of polymeric chlelating agents per se or in combination an alkaline detergent salt or salts. However the amount of the polymer that is used in accordance with these patents is directly controlled by the degree of hardness of the water in which the dishwashing composition is to be utilized; for such amount has to be sufficient for purposes of chlelating both the calcium and magnesium ions that are present. Thus the primary function of these agents has been to soften the water in which the dishes, glassware, etc. are to be washed by sequestering those metal cations which cause the hardness of such water. But this requires, for relatively hard water of around 300 ppm or higher of those cations causing such water to be hard, a high polymeric or polyelectrolyte concentration to be present in the composition of the ultimate dishwashing product that is employed.
Accordingly it is the purpose of the instant invention to provide a machine dishwashing composition employing a low amount of phosphorus compounds, i.e. less than 20 percent by weight, and also only requiring a relatively small amount of polymeric chelating agent even in the presence of hard water, the hardness approaching 300 ppm.